It has been established that the majority of lymphocytic lymphomas are proliferative neoplasms of the B lymphocyte series. The identity of the cell or cells that predominate in "histiocytic" lymphomas has not been established. We wish to perform direct studies on cells released from fresh histiocytic tumors. Cell identification studies will include E rosette, C3 receptor, membrane Ig and IgG receptor tests. In addition, H3-D-glucosamine incorporation when test cells are incubated with lymphokine and tests for macrophage participation in lymphoproliferative responses will be tested. H3-thymidine incorporation by tissue cells when cultured with plant mitogens and allogeneic leukocytes will be measured. We have shown that immune regulation becomes deranged by an excess of suppressor lymphocyte activity with advanced Hodgkin's disease. Because we have recently developed more definitive techniques for measuring suppressor cell activity in the mixed leukocyte reaction we wish to take a closer look at this abnormality. Derangement of immune regulation suggests the presence of coexistent thymic dysfunction, long suspected of being present with Hodgkin's disease. We have recently developed a quantitative, functionally specific and sensitive bioassay for thymic activity based upon the induction of Thy 1.2 antigen on incubated nude mouse precursor cells. This test readily detects thymic activity in mouse serum and is applicable for use in human studies. Thus, our studies on immune regulation can include tests for suppressor cell and serum thymic biological activities. Results obtained with Hodgkin's disease will be compared with results obtained on healthy subjects and patients with B cell and T cell series neoplasms.